The present invention relates to a preservative-bearing gelatinous material and method of using same to preserve wooden railroad cross ties.
Wooden railroad cross ties are made decay resistant by forcing a material such as creosote into the wood cell structure under relatively high pressure. This protects the exterior wood layer but the interior is not penetrated by the creosote and is subject to attack by decay fungi whenever the exterior layer is split, cracked, abraded away or otherwise structurally compromised. Penetration of the treated exterior is common after extended service use as a result of weathering and also as a result of what is known as spike kill and plate cut.
Weathering typically causes weather checking in the form of splits or cracks running in the direction of the wood grain. These cracks provide passages for moisture to travel under the tie plate supporting the rail and into the tie spike holes and checks.
Spike kill is the mechanical enlargement of spike holes caused by cyclical train loadings on the rail, the spike and the tie plate, the relative movement between these components eventually enlarges the spike hole and exposes the untreated tie wood. This relative movement also causes plate cut, which wears or cuts away the tie at the interface between the tie plate and tie. This action tends to abrade away the treated exterior wood layer and exposes the tie interior to the intrusion of moisture and fungi spores.
Soon after railroad ties are put into service moisture sites become established, particularly in the central portion of the interface between the tie and the tie plate. This central portion never seems to dry. As a consequence, the presence of moisture and the temperature elevation brought on by exposure to the sun serve as an incubator for the growth of decay fungi. The natural balance of food, moisture and temperature accelerates destruction of the wood cells and exaggerates spike kill and plate cut in a cycle which eventually results in premature failure and costly replacement of the ties.
Osmose Incorporated, in U.S. Pat. Nos. 5,236,711 and 5,043,225, disclosed in its summary of the invention xe2x80x9ca thin preservative-bearing pad that is placed between the cross tie and the tie plate either at the time of the original laying of rail or during any subsequent relaying.xe2x80x9d The pad consists of a suspension of a water-soluble fungicide in a binder sandwiched between two layers of a porous hydrophilic backing material. The use of the pad relies on the omni-present moisture found under the tie plate to leach the active ingredients, like sodium fluoride, out of the pad and help diffuse them throughout the adjacent section of wood.
That product, however, has been improved with the present invention because it now does not require a porous hydrophilic backing material and is easier to apply to the wood surface.
The general purpose of this invention is to provide an improved apparatus and method of preserving the vulnerable area of a railroad cross tie near the interface of the tie and the tie plate. To attain this purpose the invention provides a thin preservative-bearing gelatinous material that is placed between the cross tie and the tie plate either at the time of the original laying of rail or during any subsequent relaying. No extra equipment is needed and only a negligible amount of labor is required to simply place the gelatinous material on the adzed surface of the cross tie prior to the mounting or remounting of the rail. The presence of the gelatinous material poses absolutely no resistance to the subsequent driving of the spikes into the tie and is thin enough so as not to pose any rail alignment problems. The use of the gelatinous material relies on the moisture found under the tie plate to leach the active ingredients out of the material and help diffuse them throughout the adjacent section of wood. In addition, the unloading and loading of the tie plate by the passing of a train forces moisture into and out of the gelatinous material to further promote the leaching action. The inert components of the gelatinous material are completely biodegradable and will not pose an environmental problem at the end of the material""s service life.